ANALYSIS OF THE NATURAL AND ARTIFICIAL WEATHERING OF A WOOD COATING BY MEASUREMENT OF THE GLASS-TRANSITION TEMPERATURE

Weathering of wood coating systems is often only followed by visual ob servations which are very subjective. This is the reason why the natur al and artificial weathering of an alkyl based wood surface finish has been studied by measuring a quantifiable parameter. This parameter, n amely the glass transition temperature (T-g) of the polymer constituti ng the finish, has been measured as a function of time. For both weath ering cycles tested, T-g variations are the same: an increase in T-g d uring the first steps or weathering followed by a stabilization is obs erved. An equation is proposed to describe these variations. It allows the determination of time constants and also the acceleration produce d by the artificial weathering. From this equation, reaction rates of curing can be calculated for both weathering cycles tested and for eac h wood species on which the coating has been applied, This work valida tes the performance of the artificial weathering device used.